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Modelos para determinação dos parâmetros da equação de van Genuchten para um Cambissolo Models for determination of parameters of van Genuchten equation for a Cambisol

Authors: Carlos R. de Mello; Geraldo C. de Oliveira; Daniel F. Ferreira; José M. de Lima; Diego Lopes;

Modelos para determinação dos parâmetros da equação de van Genuchten para um Cambissolo Models for determination of parameters of van Genuchten equation for a Cambisol

Abstract

Com este trabalho, objetiva-se a geração de modelos matemáticos para predição dos 4 parâmetros da equação de van Genuchten (tetaR, tetaS, alfa e n) e para a umidade correspondente à capacidade de campo em função dos atributos areia, argila, matéria orgânica e densidade do solo, ambas de fácil e rotineira determinação em laboratório, além da profundidade. Coletaram-se 36 amostras não deformadas e deformadas nas profundidades de 0 a 30, 30 a 60 e 60 a 90 cm, em Cambissolo originado de gnaisse, determinando-se as umidades correspondentes às tensões de 2, 6 e 10 kPa em mesa de tensão e as referentes a 33, 100, 500 e 1500 kPa, em câmara de Richards. Para ajuste dos modelos, trabalhou-se com o programa SAS for Windows, com a rotina Proc Reg, e procedimento Backward, para selecionar as variáveis significativamente diferentes de zero num certo nível de probabilidade. Para avaliação dos modelos, consideraram-se o coeficiente de determinação e os erros de predição, tanto para os parâmetros estimados quanto para as umidades geradas pela equação de van Genuchten ajustada com os parâmetros estimados, para cada tensão descrita acima. Constatou-se que os erros foram consideravelmente pequenos, justificando a aplicação dos modelos.This work proposes to adjust mathematical models to predict the parameters of van Genuchten equation (thetaR, thetaS, alpha and n), besides a model to predict the soil moisture corresponding to the field capacity. The models express the equation parameters as dependent variables and sand, clay, organic matter, bulk density and depth as independent variables. All independent variables can be easily and routinely determined in laboratory. The samples were collected at 12 points in and three layers (0-30; 30-60; 60-90 cm) of a Cambisol, using a Uhland sampler. The soil moisture at matric potentials of 2, 6 and 10 kPa were determined using a porous plate apparatus and those at matric potentials of 33, 100, 500 and 1500 kPa were determined using a pressure plate apparatus. The models were adjusted with the SAS for Windows program, ProcReg routine and Backward procedure to select the variables significantly different from zero at the probability level adopted. The coefficient of determination and prediction errors for the parameters predicted and soil moisture generated by van Genuchten equation adjusted with parameters predicted by models, were analyzed to evaluate the models. The coefficient of determination for models was high and the errors were small justifying the application of models.

Keywords

umidade do solo, curva característica, S, Environmental engineering, irrigação, water retention curve, Agriculture, soil moisture, TA170-171, irrigation

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selected citations
These citations are derived from selected sources.
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
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